Former Penn State defensive coordinator Jerry Sandusky was convicted on Friday of sexually abusing 10 boys. A jury found Sandusky, 68, guilty on 45 out of 48 counts against him, including multiple charges of rape and sodomy, which carry substantial prison terms. It’s likely that he will spend the rest of his life behind bars.

The verdict brings some amount of relief to the boys — who are all now adults — who came forward to testify against Sandusky. Their painful testimony described crimes of abuse and rape stretching back 15 years. But arguments by Sandusky’s defense, including character testimony by his wife maintaining his innocence and rebutting claims made by two of his accusers — she called some of them “clingy” and “conniving,” while the defense cast the victims as motivated by financial greed — makes it hard not to wonder how bystanders to Sandusky’s wrongdoing could have repeatedly ignored the signs of child abuse or may continue to defend his pedophilic behavior, even after conviction.

Blame the “just world” hypothesis, say psychologists. The theory suggests that in order to avoid psychological disintegration, humans have a fundamental need to see the world as at least somewhat fair and predictable. You might think that a strong belief in justice would increase our drive to prosecute offenders. But, paradoxically, viewing the world as a fair place, where people receive their appropriate deserts, can often lead us in the opposite direction. It elicits denial of hard-to-face realities and results in the blaming of victims for suffering that has clearly been inflicted on them by others.

The just world hypothesis was developed in the 1960s by social psychologist Melvin Lerner. Fundamentally, it’s based on the idea that believing the world is fair offers a psychological sense of comfort and security. This predisposition is strongly held: even little children are intrinsically obsessed with fairness, as parents of bickering siblings know too well.

But witnessing extreme suffering or injustice, such as that described by Sandusky’s victims, threatens our feelings of safety and predictability. It upends our entire worldview and forces us to cope with the difficult reality of a confusing, amoral and chaotic universe. Therefore, it becomes easier psychologically to blame the innocent victim. Accepting the truth would otherwise threaten onlookers’ entire psyche, not just their views about a particular event.

Child sexual abuse seems particularly likely to trigger this response: it’s such a profound betrayal of trust and innocence that no one wants to believe that anyone — let alone someone they love or admire — is capable of it. That makes it much easier to reframe seemingly clear-cut situations to view the victims as liars.

Lerner explored his theory in two classic experiments. In the first, he showed that students who were told that a fellow undergrad had won the lottery tended to characterize the winner as more hardworking than other students: in other words, he was lucky because he was good.

The second experiment was more disturbing. People watching others (actors, actually) receiving apparent electrical shocks for making mistakes tended to view the victims as more deserving of ill treatment if they were unable to escape. To feel safe, the viewers chose to believe that the shock victims were being punished because they were bad, not that they were the victims of unfair abuse. Both responses — to good and bad luck — support the idea that we believe in a just world.

More recent research has expanded on these findings. For example, one 2009 study primed participants to think either about their social connections or about themselves. When they were faced with situations that highly threatened their just-world beliefs, people who were encouraged to think about their social group were more likely to blame the victims. This finding has particular resonance for the Sandusky case because the former coach’s crimes occurred against the backdrop of a much-loved football team — the community’s intense focus on the team would have certainly vaulted thoughts of the group over those related to any one individual.

Further, a 2010 study found that when people were presented with scenarios in which a woman was either raped or robbed, they were more likely to blame the victim in the rape case. Again, this makes sense because sexual crimes tend to be much more threatening to our just-world beliefs. Psychologically, we can justify robbery — it can be viewed as a crime driven by poverty or inequality — but there is no acceptable rationalization for rape.

Another study found that when people were considering a case in which a woman was robbed, they were more likely to blame the victim if the perpetrator had not been caught. Participants were also more likely to blame rape victims if they were still suffering from the aftereffects of the crime than if they appeared to have fully recovered. In both circumstances, when justice is done — the criminal is caught, the victim recovers — there is less need to blame the victim because the situation no longer threatens the observer’s just-world perspective.

Just-world beliefs are not always bad, of course. One recent study highlighted the positive: it found that those who were primed to view the world as fair or already held such strong beliefs on their own also viewed people who had suffered as being blessed with more meaningful and enjoyable lives after overcoming the tragedy. In other words, those with a just-world view tend to believe that others’ pain is ultimately balanced out by later meaning and pleasure.

As the evidence suggests, a sense of justice is clearly important to human beings’ mental health. But whether it leads to blaming of victims or the search for meaning in pain depends on the context. Which is why fair convictions of perpetrators have wide-reaching impact: it helps not only that offender’s victims, but also similar victims who may be enduring undue blame in other cases.

Acknowledging and being mindful of the effects of our just-world beliefs may also help us carefully consider our responses to cases of sexual abuse and override our tendency to dismiss and deny.